3MM=25° high contact angle superprecision ABEC-7 (ISO P4), HX=Angular Contact-Low Shoulder On Both Rings VV=Non-Contact Seals On Both Sides. CR=Phenolic (Composition) DUL=Duplex Pair Of Bearings, Universally Ground, Light Preload.. FS637=An Example Of A Specification Number For Other Than Standard.